How can i solve bisection method to find roots just based on equations and without interval ?

use the bisection method to find the root to six correct decimal places using

Answer 1

[Walter Roberson]

That is not possible. The bisection method only works when there is an interval with the sign() of the function being different between the two endpoints.

If you need to use the bisection method then you will need to come up with endpoints somehow. That is not something that is generally possible for arbitrary "black box" functions, but becomes more possible if you are permitted to use knowledge of the function.

You know that cosine squared is between 0 and 1 for real x, and you know that the sum is 0, so you can deduce that x is between -1 and 0.